This invention relates to a pulsation reducing system for a fuel line of an internal combustion engine, especially for an automotive engine equipped with an electronic fuel injection system. In the fuel injection system, a fuel rail delivers pressurized fuel supplied from a fuel tank toward intake passages or chambers via associated fuel injectors. The fuel rail is used to simplify installation of the fuel injectors and fuel supply passages on the engine.
In particular, this invention relates to a pulsation reducing system comprising a fuel delivery rail for supplying fuel to fuel injectors, a fuel tank, and a longitudinal main fuel pipe for connecting the fuel tank to the fuel delivery rail.
As shown in the attached FIG. 14, an automobile 11 having an electronic fuel injection type engine 10 is provided with a main fuel line 13 which transfers fuel from a fuel tank 12 to the engine 10. The main fuel line 13 is usually supported on a front panel or beneath a floor panel by several clips 14.
With respect to the fuel delivery rail 15 mounted on the engine 10, there are two types; one is a return type having a return pipe and another is a non-return (returnless) type. In the return type, fuel is delivered from a conduit having a fuel passage therein to fuel injectors via cylindrical sockets and then residual fuel goes back to a fuel tank via the return pipe.
Recently, for economical reasons, use of the non-return type is increasing and new problems are arising therefrom. That is, due to pressure pulsations and shock waves which are caused by reciprocal movements of a fuel pump (plunger pump) and injector spools, the fuel delivery rail and its parts are vibrated thereby emitting uncomfortable noise. Further, this vibration and noise are transmitted through the clips 14, front panel and floor panel, to the driver and assistant.
In order to reduce the vibration and noise, several anti-vibration rubber clips or elastomer clips are supplied. However, some vibration and noise still remain without being eliminated.
The frequency components of the remaining vibration (pulsation) are considered as standing waves (stationary waves) which arise in the fuel delivery rail and continuously repeat internal reflection thereby keeping up. Further, the power level of the standing waves are considered as depending upon the length and flexibility of the fuel delivery rail.
Japanese Utility Model unexamined publication No. 62-26561 entitled “Fuel injection device of an internal combustion engine” discloses a pulsation damping tube comprising an elastomer member of which volume expands and shrinks due to the fuel pressure pulsations. However, this type of damping tube cannot provide a sufficient effect to the standing waves emitted from the fuel delivery rail.
Japanese Patent unexamined publication No. 2002-106438 entitled “Pulsation absorbing system for fuel piping” discloses a pulsation absorbing container comprising a metallic, synthetic resin or elastomer member arranged in the piping so as to eliminate the emission of the noise. However, this type of absorbing container is very expensive.
Japanese Patent No. 2777884 entitled “Connector for connecting a small pipe” discloses a quick-joint connector which can be used for connecting a small metallic or plastic pipe having an outside diameter less than 20 mm.